Salt suitable for an acid generator and a chemically amplified resist composition containing the same

ABSTRACT

The present invention provides a salt of the formula (I): 
                         
wherein X represents divalent or trivalent residue of acyclic hydrocarbon having 1 to 30 carbon atoms or divalent or trivalent residue of hydrocarbon having 3 to 30 carbon atoms which contains monocyclic or bicyclic ring, wherein —CH 2 — in the hydrocarbon may be substituted with —O— and one or more hydrogen atom in X is optionally substituted with alkoxy group having 1 to 6 carbon atoms, perfluoroalkyl group having 1 to 4 carbon atoms, hydroxyalkyl group having 1 to 6 carbon atoms, hydroxyl group or cyano group; Q 1  and Q 2  each independently represent fluorine atom or perfluoroalkyl group having 1 to 6 carbon atoms; A +  represents organic counter ion; Y represents hydroxyl group, cyano group or methoxy group; and n shows 1 or 2.
 
     The present invention also provides a chemically amplified resist composition comprising the salt of the formula (I).

This nonprovisional application claims priority under 35 U.S.C. §119(a)on Patent Application No. 2005-314037 filed in JAPAN on Oct. 28, 2005,the entire contents of which are hereby incorporated by reference.

FIELD OF THE INVENTION

The present invention relates to a salt suitable for an acid generatorused for a chemical amplification type resist which is used in fineprocessing of semiconductors, and a chemically amplified resistcomposition containing the salt.

BACKGROUND OF THE INVENTION

A chemically amplified resist composition used for semiconductormicrofabrication employing a lithography process contains an acidgenerator comprising a compound generating an acid by irradiation.

In semiconductor microfabrication, it is desirable to form patternshaving high resolution and, and it is expected for a chemicallyamplified resist composition to give such patterns.

Recently, a chemically amplified resist composition containingtriphenylsulfonium 1-adamantanemethoxycarbonyldifluoromethansulfonate,p-tolyldiphenylsulfonium perfluorooctanesulfonate, and the like areproposed (e.g. JP2004-4561-A), and a salt providing a chemicallyamplified resist composition giving patterns having higher resolution.

SUMMARY OF THE INVENTION

Objects of the present invention are to provide a salt suitable for anacid generator capable of providing chemically amplified resistcompositions giving patterns having better resolution and to provide aprocess for producing the salt.

Another objects of the present invention are to provide syntheticintermediates for the salts and to provide a process for producing thesynthetic intermediates or the salts.

Still another object of the present invention are to provide achemically amplified resist composition containing the salts.

These and other objects of the present invention will be apparent fromthe following description.

The present invention relates to the followings:

<1> A salt of the formula (I):

wherein X represents divalent or trivalent residue of acyclichydrocarbon having 1 to 30 carbon atoms or divalent or trivalent residueof hydrocarbon having 3 to 30 carbon atoms which contains monocyclic orbicyclic ring, wherein —CH₂— in the hydrocarbon may be substituted with—O— and one or more hydrogen atom in X is optionally substituted withalkoxy group having 1 to 6 carbon atoms, perfluoroalkyl group having 1to 4 carbon atoms, hydroxyalkyl group having 1 to 6 carbon atoms,hydroxyl group or cyano group; Q¹ and Q² each independently representfluorine atom or perfluoroalkyl group having 1 to 6 carbon atoms; A⁺represents organic counter ion; Y represents hydroxyl group, cyano groupor methoxy group; and n shows 1 or 2. Hereinafter, the salt of theformula (I) is also referred to as Salt (I).<2> The salt according to <1>, wherein X is divalent or trivalentresidue of alkane having 1 to 30 carbon atoms, or divalent or trivalentresidue of monocyclic hydrocarbon or of bicyclic hydrocarbon having 3 to30 carbon atoms, wherein —CH₂— in the alkane may be substituted with —O—and one or more hydrogen atom in X is optionally substituted with alkoxygroup having 1 to 6 carbon atoms, perfluoroalkyl group having 1 to 4carbon atoms, hydroxyalkyl group having 1 to 6 carbon atoms, hydroxylgroup or cyano group.<3> The salt according to <2>, wherein the divalent or trivalent residueof monocyclic or bicyclic hydrocarbon in X is divalent or trivalentresidue of monocycloalkane or bicycloalkane.<4> The salt according to any of <1> to <3>, wherein A⁺ is at least onecation selected from the group consisting of the formula (IIe), theformula (IIb), the formula (IIc) and the formula (IId):a cation of the formula (IIe):

wherein P²⁵, P²⁶ and P²⁷ each independently represent alkyl group having1 to 30 carbon atoms or cyclic hydrocarbon group having 3 to 30 carbonatoms, wherein one or more hydrogen atom in the alkyl group isoptionally substituted with hydroxyl group, alkoxy group having 1 to 12carbon atoms or cyclic hydrocarbon group having 3 to 12 carbon atoms andwherein one or more hydrogen atom in the cyclic hydrocarbon group isoptionally substituted with hydroxyl group, alkyl group having 1 to 12carbon atoms or alkoxy group having 1 to 12 carbon atoms,a cation of the formula (IIb):

wherein P⁴ and P⁵ each independently represent hydrogen atom, hydroxylgroup, alkyl group having 1 to 12 carbon atoms or alkoxy group having 1to 12 carbon atoms,a cation of the formula (IIc):

wherein P⁶ and P⁷ each independently represent alkyl having 1 to 12carbon atoms or cycloalkyl having 3 to 12 carbon atoms, or P⁶ and P⁷bond to form divalent acyclic hydrocarbon group having 3 to 12 carbonatoms which forms a ring together with the adjacent S⁺, and one or more—CH₂— in the divalent acyclic hydrocarbon group is optionallysubstituted with —CO—, —O— or —S—, P⁸ represents hydrogen, P⁹ representsalkyl having 1 to 12 carbon atoms, cycloalkyl having 3 to 12 carbonatoms or aromatic ring group optionally substituted, or P⁸ and P⁹ bondto form divalent acyclic hydrocarbon group which forms 2-oxocycloalkyltogether with the adjacent —CHCO—, and one or more —CH₂— in the divalentacyclic hydrocarbon group is optionally substituted with —CO—, —O— or—S—,a cation of the formula (IId):

wherein P¹⁰, P¹¹, P¹², P¹³, P¹⁴, P¹⁵, P¹⁶, P¹⁷, P¹⁸, P¹⁹, P²⁰ and P²¹each independently represent hydrogen atom, hydroxyl group, alkyl grouphaving 1 to 12 carbon atoms or alkoxy group having 1 to 12 carbon atoms,B represents sulfur atom or oxygen atom, and m shows 0 or 1.<5> The salt according to <4>, wherein the cation of the formula (IIe)is a cation of the formula (IIf), (IIg) or (IIh):

wherein P²⁸, P²⁹ and P³⁰ each independently represent alkyl group having1 to 20 carbon atoms or cyclic hydrocarbon group having 3 to 30 exceptphenyl group, wherein one or more hydrogen atom in the alkyl group isoptionally substituted with hydroxyl group, alkoxy group having 1 to 12carbon atoms or cyclic hydrocarbon group having 3 to 12 carbon atoms andwherein one or more hydrogen atom in the cyclic hydrocarbon group isoptionally substituted with hydroxyl group, alkyl group having 1 to 12carbon atoms or alkoxy group having 1 to 12 carbon atoms; and P³¹, P³²P³³, P³⁴, P³⁵ and P³⁶ each independently represent hydoxyl group, alkylgroup having 1 to 12 carbon atoms, alkoxy group having 1 to 12 carbonatoms or cyclic hydrocarbon group having 3 to 12 carbon atoms, and l, k,j, i, h and g each independently show an integer of 0 to 5.<6> The salt according to <4>, wherein the cation of the formula (IIe)is a cation of the formula (IIa):

wherein P¹, P² and P³ each independently represent hydrogen atom,hydroxyl group, alkyl group having 1 to 12 carbon atoms or alkoxy grouphaving 1 to 12 carbon atoms.<7> The salt according to <6>, wherein the cation of the formula (IIa)is a cation of the formula (IIIe):

wherein P²², P²³ and P²⁴ each independently represent hydrogen atom oralkyl group having 1 to 4 atoms.<8> The salt according to any of <1> to <7>, wherein each of Q¹ and Q²is independently fluorine atom or trifluoromethyl group.<9> The salt according to any of <2> to <8>, wherein X is divalent ortrivalent residue of alkane having 1 to 30 carbon atoms, of cycloalkanehaving 3 to 10 carbon atoms or of norbornane, wherein —CH₂— in thealkane may be substituted with —O— and one or more hydrogen atom in X isoptionally substituted with alkoxy group having 1 to 6 carbon atoms,perfluoroalkyl group having 1 to 4 carbon atoms, hydroxyalkyl grouphaving 1 to 6 carbon atoms, hydroxyl group or cyano group; Q¹ and Q² areboth fluorine atoms; Y is hydroxyl group; and n shows 1.<10> The salt according to <1>, wherein the salt is the one of theformula (IIIa), (IIIb) or (IIIc);

wherein P²², P²³ and P²⁴ have the same meanings as defined above.<11> An ester compound of the formula (IV)

wherein M represents Li, Na, K or Ag, Q¹, Q², Y and n have the samemeanings as defined above.<12> The composition according to <11>, wherein each of Q¹ and Q² isindependently fluorine atom or trifluoromethyl group.<13> A process for producing an ester compound of the formula (IV),which comprises reacting an alcohol compound of the formula (V)HOCH₂XY_(n)  (V)wherein X, Y and n have the same meanings as defined above,with a carboxylic acid compound of the formula (VI)

wherein M, Q¹ and Q² have the same meanings as defined above.<14> A process for producing Salt (I), which comprises reacting an estercompound of the formula (IV) with a compound of the formula (VII)A⁺Z⁻  (VII)wherein Z represents F, Cl, Br, I, BF₄, AsF₆, PF₆ or ClO₄, and A⁺ hasthe same meaning as defined above.<15> A chemically amplified resist composition comprising Salt (I), anda resin which contains a structural unit having an acid-labile group andwhich itself is insoluble or poorly soluble in an alkali aqueoussolution but becomes soluble in an alkali aqueous solution by the actionof an acid.<16> The composition according to <15>, wherein each of Q¹ and Q² isindependently fluorine atom or trifluoromethyl group.<17> The composition according to <15> or <16>, wherein the resincontains a structural unit derived from a monomer having a bulky andacid-labile group.<18> The composition according to <17>, wherein the bulky andacid-labile group is 2-alkyl-2-adamantyl group or1-(1-adamantyl)-1-alkylalkyl group.<19> The composition according to <17>, wherein the monomer having bulkyand acid-labile group is 2-alkyl-2-adamantyl (meth)acrylate,1-(1-adamantyl)-1-alkylalkyl (meth)acrylate, 2-alkyl-2-adamantyl5-norbornene-2-carboxylate, 1-(1-adamantyl)-1-alkylalkyl5-norbornene-2-carboxylate, 2-alkyl-2-adamantyl α-chloroacrylate or1-(1-adamantyl)-1-alkylalkyl α-chloroacrylate.<20> The composition according to any of <15> to <19>, wherein thecomposition further comprises a basic compound.<21> The composition according to any of <15> to <20>, wherein X isdivalent or trivalent residue of alkane having 1 to 30 carbon atoms, ordivalent or trivalent residue of monocyclic hydrocarbon or of bicyclichydrocarbon having 3 to 30 carbon atoms, wherein —CH₂— in the alkane maybe substituted with —O— and one or more hydrogen atom in X is optionallysubstituted with alkoxy group having 1 to 6 carbon atoms, perfluoroalkylgroup having 1 to 4 carbon atoms, hydroxyalkyl group having 1 to 6carbon atoms, hydroxyl group or cyano group.<22> The composition according to <21>, wherein the divalent ortrivalent residue of monocyclic or bicyclic hydrocarbon in X is divalentor trivalent residue of monocycloalkane or bicycloalkane.<23> The composition according to any of <15> to <22>, wherein A⁺ is atleast one cation selected from the group consisting of the formula(IIe), the formula (IIb), the formula (IIc) and the formula (IId).<24> The composition according to <23>, wherein the cation of theformula (IIe) is a cation of the formula (IIf), (IIg) or (IIh).<25> The composition according to <23>, wherein the cation of theformula (IIe) is a cation of the formula (IIa).<26> The composition according to <25>, wherein the cation of theformula (IIa) is a cation of the formula (IIIe)<27>The composition according to <21>, wherein X is divalent ortrivalent residue of alkane having 1 to 30 carbon atoms, of cycloalkanehaving 3 to 10 carbon atoms or of norbornane, wherein —CH₂— in thealkane may be substituted with —O— and one or more hydrogen atom in X isoptionally substituted with alkoxy group having 1 to 6 carbon atoms,perfluoroalkyl group having 1 to 4 carbon atoms, hydroxyalkyl grouphaving 1 to 6 carbon atoms, hydroxyl group or cyano group; Q¹ and Q² areboth fluorine atoms; Y is hydroxyl group; and n shows 1.<28> The composition according to any of <15> to <20>, wherein the saltis the one of the formula (IIIa), (IIIb) or (IIIc).

DESCRIPTION OF PREFERRED EMBODIMENTS

The present invention provides Salt (I).

X in the formulae (I), (IV) and (V) represents divalent or trivalentresidue of acyclic hydrocarbon having 1 to 30 carbon atoms or divalentor trivalent residue of hydrocarbon having 3 to 30 carbon atoms whichcontains monocyclic or bicyclic ring. The —CH₂— in the hydrocarbon maybe substituted with —O—. One or more hydrogen atom in X is optionallysubstituted with alkoxy group having 1 to 6 carbon atoms, perfluoroalkylgroup having 1 to 4 carbon atoms, hydroxyalkyl group having 1 to 6carbon atoms, hydroxyl group or cyano group.

It is preferred that X is divalent or trivalent residue of alkane having1 to 30 carbon atoms, or divalent or trivalent residue of monocyclichydrocarbon or of bicyclic hydrocarbon having 3 to 30 carbon atoms,wherein —CH₂— in the alkane may be substituted with —O— and one or morehydrogen atom in X is optionally substituted with alkoxy group having 1to 6 carbon atoms, perfluoroalkyl group having 1 to 4 carbon atoms,hydroxyalkyl group having 1 to 6 carbon atoms, hydroxyl group or cyanogroup. The alkane may be linear or branched. As the monocyclichydrocarbon, monocycloalkane is preferred, and the monocycloalkane isalso simply referred to as cycloalkane. As the bicyclic hydorcarbon,bicycloalkane is preferred.

Examples of X include

and the like. In each of the formulae above, a straight line with anopen end shows a bond which is extended from an adjacent carbon atom andwhich does not specifies a group to be bonded but should bond to —CH₂—or Y in the formula (I), (IV) or (V).

In X, the divalent or trivalent residue of alkane having 1 to 30 carbonatoms, the divalent or trivalent residue of cycloalkane having 3 to 30carbon atoms and the divalent or trivalent residue of norbornane aremore preferred. The —CH₂— in the alkane or cycloalkane may besubstituted with —O—, and one or more hydrogen atom in the alkane,cycloalkane and norbornane is optionally substituted with alkoxy grouphaving 1 to 6 carbon atoms, perfluoroalkyl group having 1 to 4 carbonatoms, hydroxyalkyl group having 1 to 6 carbon atoms, hydroxyl group orcyano group. The cycloalkane preferably has 3 to 10 carbon atoms.

Y represents hydroxyl group, cyano group or methoxy group and n, numberof Y, is 1 or 2. When n is 1, X is divalent group, and when n is 2, X istrivalent group. It is preferred that Y is hydroxyl group and n is 1.

Q¹ and Q² each independently represent fluorine atom or perfluoroalkylgroup having 1 to 6 carbon atoms such as trifluoromethyl group,pentafluoroethyl group, heptafluoropropyl group, nonafluorobutyl group,undecafluoropentyl group, tridecafluorohexyl group, and the like. As Q¹and Q², fluorine atom and trifluoromethyl group are preferred.

Specific examples of anion part of the Salt (I) include the followings:

A⁺ in the formulae (I) and (VII) represents organic counter ion.Examples thereof include the cations of the formulae (IIe), (IIb), (IIc)and (IId).

In the cation of the formula (IIe), P²⁵, P²⁶ and P²⁷ each independentlyrepresent alkyl group having 1 to 30 carbon atoms or cyclic hydrocarbongroup having 3 to 30 carbon atoms. One or more hydrogen atom in thealkyl group in the formula (IIe) is optionally substituted with hydroxylgroup, alkoxy group having 1 to 12 carbon atoms or cyclic hydrocarbongroup having 3 to 12 carbon atoms and one or more hydrogen atom in thecyclic hydrocarbon group in the formula (IIe) is optionally substitutedwith hydroxyl group, alkyl group having 1 to 12 carbon atoms or alkoxygroup having 1 to 12 carbon atoms.

Examples of the alkyl group in the formula (IIe) include methyl group,ethyl group, propyl group, isopropyl group, n-butyl group, sec-butylgroup, tert-butyl group, pentyl group, hexyl group, octyl group,2-ethylhexyl group, and the like, and examples of the alkoxy groupinclude methoxy group, ethoxy group, propoxy group, butoxy group,hexyloxy group, octyloxy group, 2-ethylhexyloxy group, and the like.Examples of the cyclic hydrocarbon group include cyclopentyl group,cyclohexyl group, adamantyl group, bicyclohexyl group, phenyl group,naphtyl group, fluorenyl group, biphenyl group, and the like.

In the cation of the formula (IIe), cations of the formulae (IIf), (IIg)and (IIh) are preferred. In the cations of the formulae (IIf), (IIg) and(IIh), P²⁸, P²⁹ and P³⁰ each independently represent alkyl group having1 to 20 carbon atoms or cyclic hydrocarbon group having 3 to 30 exceptphenyl group. One or more hydrogen atom in the alkyl group in theformulae (IIf), (IIg) and (IIh) is optionally substituted with hydroxylgroup, alkoxy group having 1 to 12 carbon atoms or cyclic hydrocarbongroup having 3 to 12 carbon atoms. One or more hydrogen atom in thecyclic hydrocarbon group in the formulae (IIf), (IIg) and (IIh) isoptionally substituted with hydroxyl group, alkyl group having 1 to 12carbon atoms or alkoxy group having 1 to 12 carbon atoms. Examples ofthe alkyl group, alkoxy group and cyclic hydrocarbon group include thesame groups as mentioned in the formula (IIe) above.

P³¹, P³² P³³, P³⁴, P³⁵ and P³⁶ each independently represent hydoxylgroup, alkyl group having 1 to 12 carbon atoms, alkoxy group having 1 to12 carbon atoms or cyclic hydrocarbon group having 3 to 12 carbon atoms,and l, k, j, i, h and g each independently show an integer of 0 to 5.Examples of the alkyl group, alkoxy group and cyclic hydrocarbon groupinclude the sane groups as mentioned in the formula (IIe) above.

In the cation of the formula (IIe), the one of the formula (IIa) is morepreferred. In the cation of the formula (IIa), P¹, P² and P³ eachindependently represent hydrogen atom, hydroxyl group, alkyl grouphaving 1 to 12 carbon atoms or alkoxy group having 1 to 12 carbon atoms.

Examples of the alkyl group and alkoxy group in the formula (IIa)include the same groups as mentioned in the formula (IIe) above.

In the cation of the formula (IIa), the one of the formula (IIIe) aboveis preferred for the easiness of production.

In the cation of the formula (IIb), P⁴ and P⁵ each independentlyrepresent hydrogen atom, hydroxyl group, alkyl group having 1 to 12carbon atoms or alkoxy group having 1 to 12 carbon atoms. Examples ofthe alkyl group and alkoxy group include the same groups as mentioned inthe formula (IIe) above.

In the cation of the formula (IIc), P⁶ and P⁷ each independentlyrepresent alkyl having 1 to 12 carbon atoms or cycloalkyl having 3 to 12carbon atoms, or P⁶ and P⁷ bond to form divalent acyclic hydrocarbongroup having 3 to 12 carbon atoms which forms a ring together with theadjacent S⁺, and at least one —CH₂— in the divalent acyclic hydrocarbonmay be substituted with —CO—, —O— or —S—.

P⁸ represents hydrogen, P⁹ represents alkyl having 1 to 12 carbon atoms,cycloalkyl having 3 to 12 carbon atoms or aromatic ring group optionallysubstituted, or P⁸ and P⁹ bond to form divalent acyclic hydrocarbongroup which forms 2-oxocycloalkyl together with the adjacent —CHCO—, andone or more —CH₂— in the divalent acyclic hydrocarbon group isoptionally substituted with —CO—, —O— or —S—.

In P⁶, P⁷ and P⁹, specific examples of the alkyl group include methylgroup, ethyl group, propyl group, isopropyl group, butyl group,tert-butyl group, pentyl group, hexyl group, and the like, and specificexamples of the cycloalkyl group include cyclopropyl group, cyclobutylgroup, cyclopentyl group, cyclohexyl group, cycloheptyl group,cyclodecyl group, and the like. Specific examples of the divalentacyclic hydrocarbon group having 3 to 12 carbon atoms formed by bondingP⁶ and P⁷ include trimethylene group, tetramethylene group,pentamethylene group, and the like, and specific examples of the ringgroup formed by adjacent S⁺ and divalent acyclic hydrocarbon group by P⁶and P⁷ include pentamethylenesulfonio group, tetramethylenesulfoniogroup, oxybisethylenesulfonio group, and the like. In P⁹, specificexamples of the aromatic ring group include phenyl, tolyl, xylyl,naphtyl and the like. Specific examples of the divalent acyclichydrocarbon group formed by bonding P⁸ and P⁹ include methylene group,ethylene group, trimethylene group, tetramethylene group, pentamethylenegroup, and the like, and specific examples of the 2-oxocycloalkyl formedby bonding P⁸ and P⁹ together with the adjacent —CHCO— include2-oxocyclohexyl, 2-oxocyclopentyl and the like.

In the cation of the formula (IId), P¹⁰, P¹¹, P¹², P¹³, P¹⁴, P¹⁵, P¹⁶,P¹⁷, P¹⁸, P¹⁹, P²⁰ and P²¹ each independently represent hydrogen atom,hydroxyl group, alkyl group having 1 to 12 carbon atoms or alkoxy grouphaving 1 to 12 carbon atoms, B represents sulfur atom or oxygen atom,and m represents 0 or 1. Examples of the alkyl group and alkoxy groupinclude the same groups as mentioned in the formula (IIe) above.

Specific examples of the cation of the formula (IIe) include thefollowing:

Specific examples of the formula (IIb) include the following:

Specific examples of the formula (IIc) include the following:

Specific examples of the cation of the formula (IId) include thefollowing:

As Salt (I), the salts of the formulae (IIIa), (IIIb) and (IIIc) arepreferred for providing chemically amplified resist compositions showingexcellent resolution.

P²², P²³ and P²⁴ have the same meanings as defined above.

Examples of a process for production of Salt (I) include a processcomprising reacting an ester of the formula (IV) with an onium salt ofthe formula (VII), in an inert solvent such as acetonitrile, water,methanol, chloroform and dichloromethane at a temperature of 0 to 150°C., preferably of 0 to 100° C.

The amount of the onium salt of the formula (VII) is usually 0.5 to 2mol per 1 mol of the ester of the formula (IV). Salt (I) obtained can betaken out by recrystallization when it is in crystal form or byextraction by solvents and concentration when it is in oil form.

Examples of a process for production of the ester of the formula (IV)include a process reacting an alcohol compound of the formula (V) with acarboxylic acid compound of the formula (VI).

The esterification reaction can generally be carried out by mixingmaterials in an aprotic solvent such as dichloroethane, toluene,ethylbenzene, monochlorobenzene, acetonitrile, N,N-dimethylformamide,and the like, at 20 to 200° C., preferably 50 to 150° C. In theesterification reaction, an acid catalyst or a dehydrating agent isusually added, and examples of the acid catalyst include organic acidssuch as p-toluenesulfonic acid, inorganic acids such as sulfuric acid,and the like. Examples of the dehydrating agent include1,1′-carbonyldiimidazole, N,N′-dicyclohexylcarbodiimide, and the like.

The esterification may preferably be carried out with dehydration, forexample, by Dean and Stark method as the reaction time tends to beshortened.

The amount of the carboxylic acid compound of the formula (VI) isusually 0.2 to 3 mol, preferably 0.5 to 2 mol per 1 mol of the alcoholcompound of the formula (V). The amount of the acid catalyst may becatalytic amount or the amount equivalent to solvent, and is usually0.001 to 5 mol per 1 mol of the alcohol compound of the formula (V). Theamount of the dehydrating agent is usually 0.2 to 5 mol, preferably 0.5to 3 mol per 1 mol of the alcohol compound of the formula (V).

The present chemically amplified resist composition comprises Salt (I)and a resin which contains a structural unit having an acid-labile groupand which itself is insoluble or poorly soluble in an alkali aqueoussolution but becomes soluble in an alkali aqueous solution by the actionof an acid.

Salt (I) is usually used as an acid generator, and the acid generated byirradiation to Salt (I) catalytically acts against acid-labile groups ina resin, cleaves the acid-labile-group, and the resin becomes soluble inan alkali aqueous solution. Such a composition is suitable forchemically amplified positive resist composition.

The resin used for the present composition contains a structural unithaving an acid-labile group and which itself is insoluble or poorlysoluble in an alkali aqueous solution, but acid-labile group cleave byan acid. The resin after the cleavage contains carboxylic acid residueand as a result, the resin becomes soluble in an alkali aqueoussolution.

In the present specification, “—COOR” may be described as “a structurehaving ester of carboxylic acid”, and may also be abbreviated as “estergroup”. Specifically, “—COOC(CH₃)₃” may be described as “a structurehaving tert-butyl ester of carboxylic acid”, or be abbreviated as“tert-butyl ester group”.

Examples of the acid-labile group include a structure having ester ofcarboxylic acid such as alkyl ester group in which a carbon atomadjacent to the oxygen atom is quaternary carbon atom, and alicyclicester group in which a carbon atom adjacent to the oxygen atom isquaternary carbon atom, and the like, a lactone ring group in which acarbon atom adjacent to the oxygen atom is quaternary carbon atom, andthe like.

The “quaternary carbon atom” means a “carbon atom joined to foursubstituents other than hydrogen atom”.

Examples of the acid-labile group include alkyl ester group in which acarbon atom adjacent to the oxygen atom is quaternary carbon atom suchas tert-butyl ester group; acetal type ester group such as methoxymethylester group, ethoxymethyl ester group, 1-ethoxyethyl ester group,1-isobutoxyethyl ester group, 1-isopropoxyethyl ester group,1-ethoxypropoxy ester group, 1-(2-methoxyethoxy)ethyl ester,1-(2-acetoxyethoxy)ethyl ester group, 1-[2-(1-adamantyloxy)ethoxy]ethylester group, 1-[2-(1-adamantanecarbonyloxy)ethoxy]ethyl ester group,tetrahydro-2-furyl ester and tetrahydro-2-pyranyl ester group; alicyclicester group in which a carbon atom adjacent to the oxygen atom isquaternary carbon atom, such as isobornyl ester group, 1-alkylcycloalkylester group, 2-alkyl-2-adamantyl ester group,1-(1-adamantyl)-1-alkylalkyl ester group, and the like.

Examples of structures including the ester group include ester of(meth)acrylic acid structure, ester of norbornenecarboxylic acidstructure, ester of tricyclodecenecarboxylic acid structure,tetracyclodecenecarboxylic acid structure, and the like. At least onehydrogen atom in the adamantyl group above may be substituted byhydroxyl group.

The resin used for the present composition can be obtained by additionpolymerization of monomer(s) having an acid-labile group and olefinicdouble bond.

Among the monomers, it is preferable to use those having a bulky groupsuch as alicyclic group (e.g. 2-alkyl-2-adamantyl and1-(1-adamantyl)-1-alkylalkyl), as the group dissociated by the action ofan acid, since excellent resolution is obtained when used in the presentcomposition.

Examples of such monomer containing a bulky group include2-alkyl-2-adamantyl (meth)acrylate, 1-(1-adamantyl)-1-alkylalkyl(meth)acrylate, 2-alkyl-2-adamantyl 5-norbornene-2-carboxylate,1-(1-adamantyl)-1-alkylalkyl 5-norbornene-2-carboxylate,2-alkyl-2-adamantyl α-chloroacrylate, 1-(1-adamantyl)-1-alkylalkylα-chloroacrylate and the like.

Particularly when 2-alkyl-2-adamantyl (meth)acrylate or2-alkyl-2-adamantyl α-chloroacrylate is used as the monomer for theresin component in the present composition, resist composition havingexcellent resolution tend to be obtained. Typical examples of such2-alkyl-2-adamantyl (meth)acrylate and 2-alkyl-2-adamantylα-chloroacrylate include 2-methyl-2-adamantyl acrylate,2-methyl-2-adamantyl methacrylate, 2-ethyl-2-adamantyl acrylate,2-ethyl-2-adamantyl methacrylate, 2-n-butyl-2-adamantyl acrylate,2-methyl-2-adamantyl α-chloroacrylate, 2-ethyl-2-adamantylα-chloroacrylate and the like. When particularly 2-ethyl-2-adamantyl(meth)acrylate or 2-isopropyl-2-adamantyl (meth)acrylate is used for thepresent composition, composition having excellent sensitivity and heatresistance tends to be obtained. In the present invention, two or morekind of monomers having group dissociated by the action of an acid maybe used together, if necessary.

2-Alkyl-2-adamantyl (meth)acrylate can usually be produced by reacting2-alkyl-2-adamantanol or metal salt thereof with an acrylic halide ormethacrylic halide.

The resin used for the present composition can also contain, in additionto the above-mentioned structural units having an acid-labile group,other structural unit derived from acid-stable monomer. Herein, the“structural unit derived from acid-stable monomer” means “a structuralunit not dissociated by an acid generated from Salt (I)”.

Examples of such other structural units which can be contained includestructural units derived from monomers having a free carboxyl group suchas acrylic acid and methacrylic acid, structural units derived fromaliphatic unsaturated dicarboxylic anhydrides such as maleic anhydrideand itaconic anhydride, structural units derived from 2-norbornene,structural units derived from (meth)acrylonitrile, structural unitsderived from alkyl (meth)acrylate in which a carbon atom adjacent tooxygen atom is secondary or tertiary carbon atom, structural unitsderived from 1-adamantyl (meth)acrylate, structural units derived fromstyrenes such as p- or m-hydroxystyrene, structural units derived from(meth)acryloyloxy-γ-butyrolactone having a lactone ring optionallysubstituted by alkyl, and the like. Herein, 1-adamantyl ester group is aacid-stable group though the carbon atom adjacent to oxygen atom is aquaternary carbon atom, and at least one hydrogen atom on 1-adamantyester group may be substituted by hydroxy group.

Specific examples of structural unit derived from acid-stable monomerinclude a structural unit derived from 3-hydroxyl-1-adamantyl(meth)acrylate, a structural unit derived from 3,5-dihydroxy-1-adamantyl(meth)acrylate, a structural unit derived fromα-(meth)acryloyloxy-γ-butyrolactone, a structural unit derived fromβ-(meth)acryloyloxy-γ-butyrolactone, a structural unit of the followingformula (a), a structural unit derived from the following formula (b), astructural unit derived from alicyclic compound having olefinic doublebond such as a structural unit of the following formula (c), astructural unit derived from aliphatic unsaturated dicarboxylicanhydride such as a structural unit of the formula (d), a structuralunit of the formula (e), and the like.

Particularly, to contain, in addition to the structural unit having anacid-labile group, further at least one structural unit selected fromthe group consisting of a structural unit derived from p-hydroxystyrene,a structural unit derived from m-hydroxystyrene, a structural unitderived from 3-hydroxy-1-adamantyl (meth)acrylate, a structural unitderived from 3,5-dihydroxy-1-adamantyl (meth)acrylate, a structural unitof the following formula (a) and a structural unit of the followingformula (b), in the resin in the present composition, is preferable fromthe standpoint of the adhesiveness of resist to a substrate andresolution of resist.

In the formulae (a) and (b), R¹ and R² each independently representhydrogen atom, methyl group or trifluoromethyl group and R³ and R⁴ eachindependently represent methyl group, trifluoromethyl group or halogenatom, and p and q each independently represent an integer of 0 to 3.When p represents 2 or 3, each of the R³ may be the same or differentand when q represents 2 or 3, each of the R⁴ may be the same ordifferent.

3-Hydroxy-1-adamantyl (meth)acrylate and 3,5-dihydroxy-1-adamantyl(meth)acrylate can be produced, for example, by reacting correspondinghydroxyadamantane with (meth)acrylic acid or its acid halide, and theyare also commercially available.

Further, (meth)acryloyloxy-γ-butyrolactone having a lactone ringoptionally substituted by alkyl can be produced by reactingcorresponding α- or β-bromo-γ-butyrolactone with acrylic acid ormethacrylic acid, or reacting corresponding α- orβ-hydroxy-γ-butyrolactone with acrylic halide or methacrylic halide.

As monomers to give structural units of the formulae (a) and (b),specifically listed are, for example, (meth)acrylates of alicycliclactones having hydroxyl described below, and mixtures thereof, and thelike. These esters can be produced, for example, by reactingcorresponding alicyclic lactone having hydroxyl with (meth)acrylicacids, and the production method thereof is described in, for example,JP2000-26446-A.

Examples of the (meth)acryloyloxy-γ-butyrolactone having a lactone ringoptionally substituted by alkyl include α-acryloyloxy-γ-butyrolactone,α-methacryloyloxy-γ-butyrolactone,α-acryloyloxy-β,β-dimethyl-γ-butyrolactone,α-methacryloyloxy-β,β-dimethyl-γ-butyrolactone,α-acryloyloxy-α-methyl-γ-butyrolactone,α-methacryloyloxy-α-methyl-γ-butyrolactone,β-acryloyloxy-γ-butyrolactone, β-methacryloyloxy-γ-butyrolactone,β-methacryloyloxy-α-methyl-γ-butyrolactone and the like.

In the case of KrF lithography, even in the case of using a structureunit derived from hydroxystyrene such as p- and m-hydroxystyrene, as oneof the resin components, resist composition having sufficienttransparency can be obtained. For obtaining such copolymerizationresins, the corresponding (meth)acrylic ester monomer can beradical-polymerized with acetoxystyrene and styrene, and then theacetoxy group in the structure unit derived from acetoxystyrene can bede-acetylated with an acid.

The resin containing a structural unit derived from 2-norbornene showsstrong structure because alicyclic group is directly present on its mainchain and shows a property that dry etching resistance is excellent. Thestructural unit derived from 2-norbornene can be introduced into themain chain by radical polymerization using, for example, in addition tocorresponding 2-norbornene, aliphatic unsaturated dicarboxylicanhydrides such as maleic anhydride and itaconic anhydride together. Thestructural unit derived from 2-norbornene is formed by opening of itsdouble bond, and can be represented by the formula (c). The structuralunit derived from maleic anhydride and the structural unit derived fromitaconic anhydride which are the structural unit derived from aliphaticunsaturated dicarboxylic anhydrides are formed by opening of theirdouble bonds, and can be represented by the formula (d) and the formula(e), respectively.

Here, R⁵ and R⁶ in the formula (c) each independently representhydrogen, alkyl having 1 to 3 carbon atoms, hydroxyalkyl having 1 to 3carbon atoms, carboxyl, cyano or —COOU group in which U representsalcohol residue, or R⁵ and R⁶ can bond together to form a carboxylicanhydride residue represented by —C(═O)OC(═O)—.

In R⁵ and R⁶, examples of the alkyl include methyl, ethyl, propyl andisopropyl, specific examples of hydroxyalkyl include hydroxymethyl,2-hydroxyethyl and the like.

In R⁵ and R⁶, —COOU group is an ester formed from carboxyl, and as thealcohol residue corresponding to U, for example, optionally substitutedalkyls having about 1 to 8 carbon atoms, 2-oxooxolan-3- or -4-yl and thelike are listed, and as the substituent on the alkyl, hydroxyl,alicyclic hydrocarbon residues and the like are listed.

Specific examples of the monomer used to give the structural unitrepresented by the formula (c) may include the followings;

2-norbornene,

2-hydroxy-5-norbornene,

5-norbornen-2-carboxylic acid,

methyl 5-norbornen-2-carboxylate,

2-hydroxyethyl 5-norbornen-2-carboxylate,

5-norbornen-2-methanol,

5-norbornen-2,3-dicarboxylic acid anhydride, and the like.

When U in —COOU is acid-labile group, the structural unit of the formula(c) is a structural unit having acid-labile group even if it hasnorbornene structure. Examples of monomers giving structural unit havingacid-labile group include t-butyl 5-norbornen-2-carboxylate,1-cyclohexyl-1-methylethyl 5-norbornen-2-carboxylate, 1-methylcyclohexyl5-norbornen-2-carboxylate, 2-methyl-2-adamantyl5-norbornen-2-carboxylate, 2-ethyl-2-adamantyl5-norbornen-2-carboxylate, 1-(4-methylcyclohexyl)-1-methylethyl5-norbornen-2-carboxylate, 1-(4-hydroxylcydohexyl)-1-methylethyl5-norbornen-2-carboxylate, 1-methyl-1-(4-oxocyclohexyl)ethyl5-norbornen-2-carboxylate, 1-(1-adamantyl)-1-methylethyl5-norbornen-2-carboxylate, and the like.

The resin used in the present composition preferably contains structuralunit(s) having an acid-labile group generally in a ratio of 10 to 80% bymol in all structural units of the resin though the ratio variesdepending on the kind of radiation for patterning exposure, the kind ofan acid-labile group, and the like.

When the structural units particularly derived from 2-alkyl-2-adamantyl(meth)acrylate or 1-(1-adamantyl)-1-alkylalkyl (meth)acrylate are usedas the acid-labile group, it is advantageous in dry-etching resistanceof the resist that the ratio of the structural units is 15% by mol ormore in all structural units of the resin.

When, in addition to structural units having an acid-labile group, otherstructural units having acid-stable group are contained, it ispreferable that the sum of these structural units is in the range of 20to 90% by mol based on all structural units of the resin.

When alicyclic compound having olefinic double bond and aliphaticunsaturated dicarboxylic anhydride are used as copolymerization monomer,it is preferable to use them in excess amount in view of a tendency thatthese are not easily polymerized.

In the present composition, performance deterioration caused byinactivation of acid which occurs due to post exposure delay can bediminished by adding basic compounds, particularly, basicnitrogen-containing organic compounds, for example, amines as aquencher.

Specific examples of such basic nitrogen-containing organic compoundsinclude the ones represented by the following formulae:

In the formulas, T¹² and T¹³ each independently represent a hydrogenatom, an alkyl group, a cycloalkyl group or an aryl group. The alkylgroup preferably has about 1 to 6 carbon atoms, the cycloalkyl grouppreferably has about 5 to 10 carbon atoms, and the aryl group preferablyhas about 6 to 10 carbon atoms. Furthermore, at least one hydrogen atomon the alkyl group, cycloalkyl group or aryl group may eachindependently be substituted with hydroxyl group, amino group, or alkoxygroup having 1 to 6 carbon atoms. At least one hydrogen atom on theamino group may each independently be substituted with alkyl grouphaving 1 to 4 carbon atoms.

T¹⁴, T¹⁵ and T¹⁶ each independently represent a hydrogen atom, an alkylgroup, a cycloalkyl group, an aryl group or an alkoxy group. The alkylgroup preferably has about 1 to 6 carbon atoms, the cycloalkyl grouppreferably has about 5 to 10 carbon atoms, the aryl group preferably hasabout 6 to 10 carbon atoms, and the alkoxy group preferably has about 1to 6 carbon atoms. Furthermore, at least one hydrogen atom on the alkylgroup, cycloalkyl group, aryl group or alkoxy group may eachindependently be substituted with hydroxyl group, amino group, or alkoxygroup having 1 to 6 carbon atoms. At least one hydrogen atom on theamino group may be substituted with alkyl group having 1 to 4 carbonatoms.

T¹⁷ represents an alkyl group or a cycloalkyl group. The alkyl grouppreferably has about 1 to 6 carbon atoms, and the cycloalkyl grouppreferably has about 5 to 10 carbon atoms. Furthermore, at least onehydrogen atom on the alkyl group or cycloalkyl group may eachindependently be substituted with hydroxyl group, amino group, or alkoxygroup having 1 to 6 carbon atoms. At least one hydrogen atom on theamino group may be substituted with alkyl group having 1 to 4 carbonatoms.

In the formulas, T¹⁸ represents an alkyl group, a cycloalkyl group or anaryl group. The alkyl group preferably has about 1 to 6 carbon atoms,the cycloalkyl group preferably has about 5 to 10 carbon atoms, and thearyl group preferably has about 6 to 10 carbon atoms. Furthermore, atleast one hydrogen atom on the alkyl group, cycloalkyl group or arylgroup may each independently be substituted with a hydroxyl group, anamino group, or an alkoxy group having 1 to 6 carbon atoms. At least onehydrogen atom on the amino group may each independently be substitutedwith alkyl group having 1 to 4 carbon atoms.

However, none of T¹² and T¹³ in the compound represented by the aboveformula [3] is a hydrogen atom.

A represents alkylene group, carbonyl group, imino group, sulfide groupor disulfide group. The alkylene group preferably has about 2 to 6carbon atoms.

Moreover, among T¹²-T¹⁸, in regard to those which can bestraight-chained or branched, either of these may be permitted.

T¹⁹, T²⁰ and T²¹ each independently represent a hydrogen atom, an alkylgroup having 1 to 6 carbon atoms, an aminoalkyl group having 1 to 6carbon atoms, a hydroxyalkyl group having 1 to 6 carbon atoms or asubstituted or unsubstituted aryl group having 6 to 20 carbon atoms, orT¹⁹ and T²⁰ bond to form an alkylene group which forms a lactam ringtogether with adjacent —CO—N—.

Examples of such compounds include hexylamine, heptylamine, octylamine,nonylamine, decylamine, aniline, 2-, 3- or 4-methylaniline,ethylenediamine, tetramethylenediamine, hexamethylenediamine,4,4′-diamino-1,2-diphenylethane,4,4′-diamino-3,3′-dimethyldiphenylmethane,4,4′-diamino-3,3′-diethyldiphenylmethane, dibutylamine, dipentylamine,dihexylamine, diheptylamine, dioctylamine, dinonylamine, didecylamine,N-methylaniline, piperidine, diphenylamine, triethylamine,trimethylamine, tripropylamine, tributylamine, tripentylamine,trihexylamine, triheptylamine, trioctylamine, trinonylamine,tridecylaamine, methyldibutylamine, methyldipentylamine,methyldihexylamine, methyldicyclohexylamine, methyldiheptylamine,methyldioctylamine, methyldinonylamine, methyldidecylamine,ethyldibutylamine, ethydipentylamine, ethyldihexylamine,ethydiheptylamine, ethyldioctylamine, ethyldinonylamine,ethyldidecylamine, dicyclohexylmethylamine,tris[2-(2-methoxyethoxy)ethyl]amine, triisopropanolamine,N,N-dimethylaniline, 2,6-isopropylaniline, pyridine, 4-methylpyridine,bipyridine, 2,2′-dipyridylamine, di-2-pyridyl ketone,1,2-di(2-pyridyl)ethane, 1,2-di(4-pyridyl)ethane,1,3-di(4-pyridyl)propane, 1,2-bis(2-pyridyl)ethylene,1,2-bis(4-pyridyl)ethylene, 4,4′-dipyridyl sulfide, 4,4′-dipyridyldisulfide, 1,2-bis(4-pyridyl)ethylene, 2,2′-dipicolylamine,3,3′-dipicolylamine, tetramethylammonium hydroxide,tetraisopropylammonium hydroxide, tetrabutylammonium hydroxide,tetra-n-hexylammonium hydroxide, tetra-n-octylammonium hydroxide,phenyltrimethylammonium hydroxide,3-trifluoromethylphenyltrimethylammonium hydroxide,(2-hydroxyethyl)trimethylammonium hydroxide (so-called “choline”),N-methylpyrrolidone, and the like.

Furthermore, hindered amine compounds having piperidine skeleton asdisclosed in JP-A-H11-52575 can be used as quencher.

It is preferable that the present composition contains resin componentin an amount of about 80 to 99.9% by weight and Salt (I) in an amount of0.1 to 20% by weight on the total amount of the resin component and Salt(I).

When basic compound is used as a quencher, the basic compound iscontained preferably in an amount of about 0.01 to 1 part by weight per100 parts by weight of sum of resin component and Salt (I).

The present composition can contain, if necessary, various additives insmall amount such as a sensitizer, solution suppressing agent, otherpolymers, surfactant, stabilizer, dye and the like, as long as theeffect of the present invention is not prevented.

The present composition is usually in the form of a resist liquidcomposition in which the aforementioned ingredients are dissolved in asolvent, and the resist liquid composition is to be applied onto asubstrate such as a silicon wafer by a conventional process such as spincoating. The solvent used here is sufficient to dissolve theaforementioned ingredients, have an adequate drying rate, and give auniform and smooth coat after evaporation of the solvent and, hence,solvents generally used in the art can be used. In the presentinvention, the total solid content means total content exclusive ofsolvents.

Examples thereof include glycol ether esters such as ethyl Cellosolveacetate, methyl Cellosolve acetate and propylene glycol monomethyl etheracetate; glycol ethers such as propylene glycol monomethyl ether,di(ethylene glycol) dimethyl ether; esters such as ethyl lactate, butyllactate, amyl lactate and ethyl pyruvate and the like; ketones such asacetone, methyl isobutyl ketone, 2-heptanone and cyclohexanone; cyclicesters such as γ-butyrolactone, and the like. These solvents can be usedeach alone or in combination of two or more.

A resist film applied onto the substrate and then dried is subjected toexposure for patterning, then heat-treated for facilitating a deblockingreaction, and thereafter developed with an alkali developer. The alkalideveloper used here may be any one of various alkaline aqueous solutionsused in the art, and generally, an aqueous solution oftetramethylammonium hydroxide or (2-hydroxyethyl)trimethylammoniumhydroxide (commonly known as “choline”) is often used.

It should be construed that embodiments disclosed here are examples inall aspects and not restrictive. It is intended that the scope of thepresent invention is determined not by the above descriptions but byappended Claims, and includes all variations of the equivalent meaningsand ranges to the Claims.

The present invention will be described more specifically by way ofexamples, which are not construed to limit the scope of the presentinvention. The “%” and “part(s)” used to represent the content of anycomponent and the amount of any material used in the following examplesand comparative examples are on a weight basis unless otherwisespecifically noted. The weight-average molecular weight of any materialused in the following examples is a value found by gel permeationchromatography [HLC-8120GPC Type, Column (Three Columns): TSKgelMultipore HXL-M, Solvent: Tetrahydrofuran, manufactured by TOSOHCORPORATION] using styrene as a standard reference material. Structuresof compounds were determined by NMR (GX-270 Type, or EX-270 Type,manufactured by JEOL LTD) and mass spectrometry (Liquid Chromatography:1100 Type, manufactured by Hewlett Packard, Mass Spectrometry: LC/MSDType, manufactured by Hewlett Packard).

EXAMPLE 1 Synthesis of triphenylsulfonium(2-hydroxyethoxycarbonyl)difluoromethanesulfonate

(1) 230 Parts of 30% aqueous sodium hydroxide solution was added into amixture of 100 parts of methyl difluoro(fluorosulfonyl)acetate and 250parts of ion-exchanged water in a ice bath. The added mixture was heatedand refluxed at 100° C. for 3 hours. After cooling, the cooled mixturewas neutralized with 88 parts of conc. hydrochloric acid andconcentrated to obtain 165.0 parts of sodium difluorosulfoacetate(containing inorganic salt, purity: 62.5%).

(2) 8.0 Parts of sodium difluorosulfoacetate (purity: 62.5%), 1.57 partsof ethylene glycol and 60 parts of dichloroethane were charged in avessel, 1.24 parts of sulfuric acid was added thereto, and the mixturewas refluxed for 4 hours. After concentrating the mixture to eliminatedichloroethane, 100 parts of ethyl acetate was added thereto, and theadded mixture was stirred. The stirred mixture was filtrated andconcentrated to obtain 9.25 parts of sodium salt of 2-hydroxyethyldifluorosulfoacetate.

¹H-NMR data of sodium salt of 2-hydroxyethyl difluorosulfoacetate(dimethylsulfoxide-d₆, Internal Standard: tetramethylsilane): d(ppm)3.60(q, 2H); 4.22(t, 2H); 4.82(br, 1H)

(3) 9.25 Parts of sodium salt of 2-hydroxyethyl difluorosulfoacetateobtained in (2) was dissolved in 92.5 parts of acetonitrile. 11.4 partsof triphenylsulfonium chloride and 57 parts of ion-exchanged water wereadded to the solution. After stirred for 15 hours, the stirred mixturewas concentrated and extracted first with 100 parts of and then with 50parts of chloroform. The organic layers were mixed and washed withion-exchanged water. The obtained organic layer was concentrated. Theconcentrate was washed with each of 50 parts of tert-butyl methyl etherand 50 parts of ethyl acetate and each of the solvent was decanted toobtain 5.54 parts of triphenylsulfonium(2-hydroxyethoxycarbonyl)difluoromethanesulfonate in the form of whitesolid, which is called as acid generator B1.

¹H-NMR data of acid generator B1 (dimethylsulfoxide-d₆, InternalStandard: tetramethylsilane): d(ppm)

3.58(q, 2H); 4.20(t, 2H); 4.78(t, 1H); 7.74-7.89(m, 15H)

MS(ESI(+) Spectrum): M+263.2 (C₁₈H₁₅S⁺=263.09)

MS(ESI(−) Spectrum): M−219.0 (C₄H₅F₂O₆S⁻=218.98)

EXAMPLE 2 Synthesis of triphenylsulfonium(8-hydroxyoctyloxycarbonyl)difluoromethanesulfonate

(1) 424 Parts of 30% aqueous sodium hydroxide solution was added into amixture of 500 parts of methyl difluoro(fluorosulfonyl)acetate and 750parts of ion-exchanged water in a ice bath. The added mixture was heatedand refluxed at 100° C. for 2.5 hours. After cooling, the cooled mixturewas neutralized with 440 parts of conc. hydrochloric acid andconcentrated to obtain 802.82 parts of sodium difluorosulfoacetate(containing inorganic salt, purity: 64.2%).

(2) 5.0 Parts of sodium difluorosulfoacetate (purity: 64.2%), 2.32 partsof 1,8-octane diol and 60 parts of dichloroethane were charged in avessel, 3.02 parts of p-toluenesulfonic acid (p-TsOH) was added thereto,and the mixture was refluxed for 4.5 hours. After concentrating themixture to eliminate dichloroethane, 100 parts of t-butyl methyl etherwas added thereto and washed, and then the solvent was decanted. Thewashed mixture was concentrated. 100 parts of acetonitrile was addedthereto, and the added mixture was stirred. The stirred mixture wasfiltrated and concentrated to obtain 2.82 parts of sodium salt of8-hydroxyoctyl difluorosulfoacetate. (containing diester compound,purity:41.2%)

¹H-NMR data of sodium salt of 8-hydroxyoctyl difluorosulfoacetate(dimethylsulfoxide-d₆, Internal Standard: tetramethylsilane): d(ppm)1.26-1.43(m, 10H); 1.56-1.65(m, 2H); 3.37(t, 2H); 4.19(t, 2H)

(3) 2.82 Parts of sodium salt of 8-hydroxyoctyl difluorosulfoacetateobtained in (2) was dissolved in 28.2 parts of acetonitrile. 3.19 partsof triphenylsulfonium chloride and 31.9 parts of ion-exchanged waterwere added to the solution. After stirred for 15 hours, the stirredmixture was concentrated and extracted with 50 parts of chloroformtwice. The organic layers were mixed and washed with ion-exchangedwater. The obtained organic layer was concentrated. The concentrate waswashed with of 30 parts of tert-butyl methyl ether and the solvent wasdecanted. Then the washed concentrate was extracted first with 50 partsof and then 200 parts of ethyl acetate. The organic layers were mixedand concentrated to obtain 0.73 part of triphenylsulfonium(8-hydroxyoctyloxycarbonyl)difluoromethanesulfonate in the form ofcolorless liquid, which is called as acid generator B2.

¹H-NMR data of acid generator B2 (dimethylsulfoxide-d₆, InternalStandard: tetramethylsilane): d(ppm)

1.26-1.42(m, 10H); 1.54-1.64(m, 2H); 3.38(t, 2H); 4.18(t, 2H); 4.31(t,1H); 7.75-7.90(m, 15H)

MS(ESI(+) Spectrum): M+263.2 (C₁₈H₁₅S⁺=263.09)

MS(ESI(−) Spectrum): M−303.2 (C₁₀H₁₇F₂O₆S⁻=303.07)

EXAMPLE 3 Synthesis of triphenylsulfonium((4-hydroxymethylcyclohexyl)methoxycarbonyl)-difluoromethanesulfonate

(1) 230 Parts of 30% aqueous sodium hydroxide solution was added into amixture of 100 parts of methyl difluoro(fluorosulfonyl)acetate and 250parts of ion-exchanged water in a ice bath. The added mixture was heatedand refluxed at 100° C. for 3 hours. After cooling, the cooled mixturewas neutralized with 88 parts of conc. hydrochloric acid andconcentrated to obtain 165.0 parts of sodium difluorosulfoacetate(containing inorganic salt, purity: 62.5%).

(2) 5.0 Parts of sodium difluorosulfoacetate (purity: 62.5%), 2.28 partsof 1,4-cyclohexane dimethanol and 60 parts of dichloroethane werecharged in a vessel, 3.00 parts of p-toluenesulfonic acid (p-TsOH) wasadded thereto, and the mixture was refluxed for 0.6 hour. Afterconcentrating the mixture to eliminate dichloroethane, 100 parts ofacetonitrile was added thereto and the mixture was stirred. The stirredmixture was filtrated and concentrated to obtain 6.78 parts of sodiumsalt of 4-hydroxymethylcyclohexylmethyl difluorosulfoacetate.(containing 1,4-cyclohexane dimethanol and diester)

¹H-NMR data of sodium salt of 4-hydroxymethylcyclohexylmethyldifluorosulfoacetate (dimethylsulfoxide-d₆, Internal Standard:tetramethylsilane): d(ppm) 0.76-1.01(m, 4H); 1.27(br, 1H); 1.57(br, 1H);1.73(d, 4H); 3.20(t, 2H); 4.03(d, 2H); 4.70(br, 1H)

(3) 6.78 Parts of sodium salt of 4-hydroxymethylcyclohexylmethyldifluorosulfoacetate obtained in (2) was dissolved in 67.8 parts ofacetonitrile. 6.25 parts of triphenylsulfonium chloride and 62.5 partsof ion-exchanged water were added to the solution. After stirred for 15hours, the stirred mixture was concentrated and 250 parts of chloroformwas added thereto. The added mixture was filtrated to eliminateundissolved substance. The organic layer was washed with ion-exchangedwater. The obtained organic layer was concentrated. The concentrate waswashed with 30 parts of tert-butyl methyl ether and the solvent wasdecanted. Then 10 parts of acetonitrile was added thereto and themixture was filtrated to eliminate undissolved substance. The additionand filtration were repeated two more times. The filtrated solution wasconcentrated to obtain 1.81 parts of triphenylsulfonium((4-hydroxymethylcyclohexyl)methoxycarbonyl)difluoromethanesulfonate inthe form of colorless liquid, which is called as acid generator B3.

¹H-NMR data of acid generator B3 (dimethylsulfoxide-d₆, InternalStandard: tetramethylsilane): d(ppm) 0.77-1.03(m, 4H); 1.28(br, 1H);1.57(br, 1H); 1.73(d, 4H); 3.19(t, 2H); 4.02(d, 2H); 4.35(t, 1H);7.75-7.90(m, 15H)

MS(ESI(+) Spectrum): M+263.2 (C₁₈H₁₅S⁺=263.09)

MS(ESI(−) Spectrum): M−301.0(C₁₀H₁₅F₂O₆S⁻=301.06)

EXAMPLE 4 Synthesis of triphenylsulfonium(2-(2-(2-hydroxyethoxy)ethoxy)ethoxycarbonyl)-difluoromethanesulfonate

(1) 424 Parts of 30% aqueous sodium hydroxide solution was added into amixture of 500 parts of methyl difluoro(fluorosulfonyl)acetate and 750parts of ion-exchanged water in a ice bath. The added mixture was heatedand refluxed at 100° C. for 2.5 hours. After cooling, the cooled mixturewas neutralized with 440 parts of conc. hydrochloric acid andconcentrated to obtain 802.82 parts of sodium difluorosulfoacetate(containing inorganic salt, purity: 64.2%).

(2) 5.0 Parts of sodium difluorosulfoacetate (purity: 64.2%), 2.43 partsof triethylene glycol and 60 parts of dichloroethane were charged in avessel, 3.08 parts of p-toluenesulfonic acid (p-TsOH) was added thereto,and the mixture was refluxed for 12 hours. After concentrating themixture to eliminate dichloroethane, 100 parts of t-butyl methyl etherwas added thereto and washed. Then the solvent was decanted and theresidue was filtrated. 100 Parts of acetonitrile was added thereto, andthe added mixture was stirred. The stirred mixture was filtrated andconcentrated to obtain 5.06 parts of sodium salt of2-(2-(2-hydroxylethoxy)ethoxy)ethyl difluorosulfoacetate. (containingtriethylene glycol and diester compound)

H-NMR data of sodium salt of 2-(2-(2-hydroxylethoxy)ethoxy)ethyldifluorosulfoacetate (dimethylsulfoxide-d₆, Internal Standard:tetramethylsilane): d(ppm) 3.38-3.40(m, 2H); 3.46-3.54(m, 6H);3.62-3.65(m, 2H); 4.28-4.32(m, 2H); 4.56(br, 1H)

(3) 5.06 Parts of sodium salt of 2-(2-(2-hydroxyethoxy)ethoxy)ethyldifluorosulfoacetate obtained in (2) was dissolved in 50.6 parts ofacetonitrile. 6.87 parts of triphenylsulfonium chloride and 34.3 partsof ion-exchanged water were added to the solution. After stirred for 15hours, the stirred mixture was concentrated and extracted first with 100parts of and then with 50 parts of chloroform. The organic layers weremixed and washed with ion-exchanged water. The obtained organic layerwas concentrated. The concentrate was washed with each of 20 parts oftert-butyl methyl ether and 20 parts of ethyl acetate and each of thesolvent was decanted. The washed concentrate was extracted with 200parts of ethyl acetate twice, with a mixed solvent consisting of 5 partsof acetonitrile and 200 parts of ethyl acetate, and a mixed solventconsisting of 10 parts of acetonitrile and 200 parts of ethyl acetate toobtain 0.91 part of triphenylsulfonium(2-(2-(2-hydroxyethoxy)ethoxy)ethoxycarbonyl)-difluoromethanesulfonatein the form of colorless liquid, which is called as acid generator B4.

¹H-NMR data of acid generator B4 (dimethylsulfoxide-d₆, InternalStandard: tetramethylsilane): d(ppm) 3.39-3.43(m, 2H); 3.45-3.58(m, 6H);3.63-3.66(m, 2H); 4.29-4.33(m, 2H); 4.57(t, 1H); 7.75-7.90(m, 15H)

MS(ESI(+) Spectrum): M+263.0 (C₁₈H₁₅S⁺=263.09)

MS(ESI(−) Spectrum): M−307.0 (C₈H₁₃F₂O₈S⁻=307.03)

EXAMPLE 5 Synthesis of triphenylsulfonium(2-methoxyethoxycarbonyl)difluoromethanesulfonate

(1) 424 Parts of 30% aqueous sodium hydroxide solution was added into amixture of 500 parts of methyl difluoro(fluorosulfonyl)acetate and 750parts of ion-exchanged water in a ice bath. The added mixture was heatedand refluxed at 100° C. for 2.5 hours. After cooling, the cooled mixturewas neutralized with 440 parts of conc. hydrochloric acid andconcentrated to obtain 802.82 parts of sodium difluorosulfoacetate(containing inorganic salt, purity: 64.2%).

(2) 5.0 Parts of sodium difluorosulfoacetate (purity: 64.2%), 1.23 partsof 2-methoxymethanol and 60 parts of dichloroethane were charged in avessel, 3.08 parts of p-toluenesulfonic acid (p-TsOH) was added thereto,and the mixture was refluxed for 10 hours. After concentrating themixture to eliminate dichloroethane, 100 parts of t-butyl methyl etherwas added thereto and washed. Then the solvent was decanted and theresidue was filtrated. 100 Parts of acetonitrile was added thereto, andthe added mixture was stirred. The stirred mixture was filtrated andconcentrated to obtain 1.01 parts of sodium salt of 2-methoxyethyldifluorosulfoacetate.

H-NMR data of sodium salt of 2-methoxyethyl difluorosulfoacetate(dimethylsulfoxide-d₆, Internal Standard: tetramethylsilane): d(ppm)3.27(s, 3H); 3.54-3.58(m, 2H); 4.30-4.33(m, 2H)

(3) 1.01 Parts of sodium salt of 2-methoxyethyl difluorosulfoacetateobtained in (2) was dissolved in 10.1 parts of acetonitrile. 1.18 partsof triphenylsulfonium chloride and 5.9 parts of ion-exchanged water wereadded to the solution. After stirred for 15 hours, the stirred mixturewas concentrated. The concentrate was extracted with 50 parts ofchloroform twice. The organic layers were mixed and washed withion-exchanged water. The washed organic layer was concentrated. Theconcentrate was washed with of 20 parts of tert-butyl methyl ether andthe solvent was decanted to obtain 0.84 part of triphenylsulfonium(2-methoxyethoxycarbonyl)difluoromethanesulfonate in the form of whitesolid, which is called as acid generator B5.

¹H-NMR data of acid generator B5 (dimethylsulfoxide-d₆, InternalStandard: tetramethylsilane): d(ppm) 3.27(s, 3H); 3.54-3.57(m, 2H);4.29-4.33(m, 2H);7.75-7.90(m, 15H)

MS(ESI(+) Spectrum): M+263.0 (C₁₈H₁₅S⁺=263.09)

MS(ESI(−) Spectrum): M−233.0 (C₅H₇F₂O₆S⁻=232.99)

EXAMPLE 6 Synthesis of triphenylsulfonium(2-(2-methoxyethoxy)ethoxycarbonyl)difluoromethanesulfonate

(1) 424 Parts of 30% aqueous sodium hydroxide solution was added into amixture of 500 parts of methyl difluoro(fluorosulfonyl)acetate and 750parts of ion-exchanged water in a ice bath. The added mixture was heatedand refluxed at 100° C. for 2.5 hours. After cooling, the cooled mixturewas neutralized with 440 parts of conc. hydrochloric acid andconcentrated to obtain 802.82 parts of sodium difluorosulfoacetate(containing inorganic salt, purity: 64.2%).

(2) 5.0 Parts of sodium difluorosulfoacetate (purity: 64.2%), 1.95 partsof 2-(2-methoxyethoxy)ethanol and 60 parts of dichloroethane werecharged in a vessel, 3.08 parts of p-toluenesulfonic acid (p-TsOH) wasadded thereto, and the mixture was refluxed for 12 hours. Afterconcentrating the mixture to eliminate dichloroethane, 100 parts oft-butyl methyl ether was added thereto and washed. Then the solvent wasdecanted and the residue was filtrated. 100 Parts of acetonitrile wasadded thereto, and the added mixture was stirred. The stirred mixturewas filtrated and concentrated to obtain 2.82 parts of sodium salt of2-(2-methoxyethoxy)ethyl difluorosulfoacetate.

H-NMR data of sodium salt of 2-(2-methoxyethoxy)ethyldifluorosulfoacetate (dimethylsulfoxide-d₆, Internal Standard:tetramethylsilane): d(ppm) 3.24(s, 3H); 3.41-3.45(m, 2H); 3.54-3.57(m,2H); 3.62-3.66(m,2H); 4.29-4.33(m, 2H)

(3) 2.82 Parts of sodium salt of 2-(2-methoxyethoxy)ethyldifluorosulfoacetate obtained in (2) was dissolved in 28.2 parts ofacetonitrile. 2.81 parts of triphenylsulfonium chloride and 14.0 partsof ion-exchanged water were added to the solution. After stirred for 15hours, the stirred mixture was concentrated. The concentrate wasextracted first with 100 parts of and then with 50 parts of chloroform.The organic layers were mixed and washed with ion-exchanged water. Thewashed organic layer was concentrated. The concentrate was washed withof 20 parts of tert-butyl methyl ether and the solvent was decanted toobtain 3.47 part of triphenylsulfonium(2-(2-methoxyethoxy)ethoxycarbonyl)difluoromethanesulfonate in the formof colorless liquid, which is called as acid generator B6.

H-NMR data of acid generator B6 (dimethylsulfoxide-d₆, InternalStandard: tetramethylsilane): d(ppm) 3.23(s, 3H); 3.41-3.44(m, 2H);3.53-3.57(m, 2H); 3.62-3.66(m, 2H); 4.29-4.32(m, 2H); 7.76-7.91(m, 15H)

MS(ESI(+) Spectrum): M+263.0 (C₁₈H₁₅S⁺=263.09)

MS(ESI(−) Spectrum): M−277.0 (C₇H₁₁F₂O₇S⁻=277.02)

EXAMPLE 7 Synthesis of triphenylsulfonium(2-cyanoethoxycarbonyl)difluoromethanesulfonate

(1) 424 Parts of 30% aqueous sodium hydroxide solution was added into amixture of 500 parts of methyl difluoro(fluorosulfonyl)acetate and 750parts of ion-exchanged water in a ice bath. The added mixture was heatedand refluxed at 100° C. for 2.5 hours. After cooling, the cooled mixturewas neutralized with 440 parts of conc. hydrochloric acid andconcentrated to obtain 802.82 parts of sodium difluorosulfoacetate(containing inorganic salt, purity: 64.2%).

(2) 5.0 Parts of sodium difluorosulfoacetate (purity: 64.2%), 1.15 partsof 2-cyanoethanol and 60 parts of dichloroethane were charged in avessel, 3.08 parts of p-toluenesulfonic acid (p-TsOH) was added thereto,and the mixture was refluxed for 10 hours. After concentrating themixture to eliminate dichloroethane, 100 parts of t-butyl methyl etherwas added thereto and washed. Then the solvent was decanted and theresidue was filtrated. 100 Parts of acetonitrile was added thereto, andthe added mixture was stirred. The stirred mixture was filtrated andconcentrated to obtain 2.40 parts of sodium salt of 2-cyanoethyldifluorosulfoacetate.

H-NMR data of sodium salt of 2-cyanoethyl difluorosulfoacetate(dimethylsulfoxide-d₆, Internal Standard: tetramethylsilane): d(ppm)2.94(t, 2H); 4.41(t, 2H)

(3) 2.40 Parts of sodium salt of 2-cyanoethyl difluorosulfoacetateobtained in (2) was dissolved in 24.0 parts of acetonitrile. 2.82 partsof triphenylsulfonium chloride and 14.11 parts of ion-exchanged waterwere added to the solution. After stirred for 15 hours, the stirredmixture was concentrated. The concentrate was extracted with 50 parts ofchloroform twice. The organic layers were mixed and washed withion-exchanged water. The washed organic layer was concentrated. Theconcentrate was washed with of 20 parts of tert-butyl methyl ether andthe solvent was decanted to obtain 0.71 part of triphenylsulfonium(2-cyanoethoxycarbonyl)difluoromethanesulfonate in the form of colorlessliquid, which is called as acid generator B7.

H-NMR data of acid generator B7 (dimethylsulfoxide-d₆, InternalStandard: tetramethylsilane): d(ppm) 2.94(t, 2H); 4.41(t, 2H);7.75-7.90(m, 15H)

MS(ESI(+) Spectrum): M+263.0 (C₁₈H₁₅S⁺=263.09)

MS(ESI(−) Spectrum): M−228.0 (C₅H₄F₂NO₅S⁻=227.98)

RESIN SYNTHESIS EXAMPLE 1 Synthesis of Resin A1

2-Ethyl-2-adamantyl methacrylate, 3-hydroxy-1-adamantyl methacrylate andα-methacryloyloxy-γ-butyrolactone were charged at a molar ratio of5:2.5:2.5 (20.0 parts:9.5 parts:7.3 parts), and methyl isobutyl ketonein twice weight based on all monomers was added, to prepare solution. Tothe solution was added azobisisobutyronitrile as an initiator in a ratioof 2 mol % based on all monomer molar amount, and the mixture was heatedat 80° C. for about 8 hours. Then, the reaction solution was poured intolarge amount of heptane to cause precipitation, and this operation wasrepeated three times for purification. As a result, copolymer having aweight-average molecular weight of about 9,200 was obtained. This iscalled resin A1.

EXAMPLES 1 TO 2 AND COMPARATIVE EXAMPLE 1

The following components were mixed and dissolved, further, filtratedthrough a fluorine resin filter having pore diameter of 0.2 μm, toprepare resist liquid.

<Resin>

resin A1: 10 parts

<Acid Generator>

acid generator B1: 0.21 part

acid generator B2: 0.25 part

acid generator C1: 0.25 part

<Quencher>

quencher Q1: 2,6-diisopropylaniline 0.0325 part

<Solvent>

Solvent Y1: propylene glycol monomethyl ether acetate 80.0 partspropylene glycol monomethyl ether 20.0 parts γ-butyrolactone  3.0 parts

Silicon wafers were each coated with “ARC-29A-8”, which is an organicanti-reflective coating composition available from Brewer Co., and thenbaked under the conditions: 215° C., 60 seconds, to form a 780 Å-thickorganic anti-reflective coating. Each of the resist liquids prepared asabove was spin-coated over the anti-reflective coating so that thethickness of the resulting film became 0.25 μm after drying. The siliconwafers thus coated with the respective resist liquids were each prebakedon a direct hotplate at a temperature of 130° C. for 60 seconds. Usingan ArF excimer stepper (“NSR ArF” manufactured by Nikon Corporation,NA=0.55, ⅔Annular), each wafer thus formed with the respective resistfilm was subjected to line and space pattern exposure, with the exposurequantity being varied stepwise.

After the exposure, each wafer was subjected to post-exposure baking ona hotplate at a temperature of 130° C. for 60 seconds and then to paddledevelopment for 60 seconds with an aqueous solution of 2.38 wt %tetramethylammonium hydroxide.

Each of a bright field pattern developed on the organic anti-reflectivecoating substrate was observed with a scanning electron microscope, theresults of which are shown in Table 1. The term “bright field pattern”,as used herein, means a pattern obtained by exposure and developmentthrough a reticle comprising an outer frame made of a chromium layer(light-shielding layer) and linear chromium layers (light-shieldinglayers) formed on a glass surface (light-transmitting portion) extendinginside the outer frame. Thus, the bright field pattern is such that,after exposure and development, resist layer surrounding the line andspace pattern is removed while resist layer corresponding to the outerframe is left on the outer side of the region from which the resistlayer is removed.

Effective Sensitivity:

It is expressed as the amount of exposure that the line pattern(light-shielding layer) and the space pattern (light-transmitting layer)become 1:1 after exposure through 0.13 μm line and space pattern maskand development.

Resolution:

It is expressed as the minimum size of space pattern which gave thespace pattern split by the line pattern at the exposure amount of theeffective sensitivity.

TABLE 1 No. Acid Generator Effective Sensitivity Resolution (μm) Example1 B1 27.5 0.12 Example 2 B2 30.0 0.12 Comparative C1 25.0 0.13 Example 1

Salt (I) is suitably used for an acid generator for chemically amplifiedpositive resist composition. The present composition provides excellentresist pattern in resolution and is especially suitable for ArF excimerlaser lithography, KrF excimer laser lithography and ArF immersionlithography.

1. A salt of the formula (I):

wherein X represents divalent or trivalent residue of acyclichydrocarbon having 1 to 30 carbon atoms or divalent or trivalent residueof hydrocarbon having 3 to 30 carbon atoms which contains monocyclic orbicyclic ring, wherein —CH₂— in the hydrocarbon may be substituted with—O— and one or more hydrogen atom in X is optionally substituted withalkoxy group having 1 to 6 carbon atoms, perfluoroalkyl group having 1to 4 carbon atoms, hydroxyalkyl group having 1 to 6 carbon atoms,hydroxyl group or cyano group; Q¹ and Q² each independently representfluorine atom or perfluoroalkyl group having 1 to 6 carbon atoms; A⁺represents organic counter ion; Y represents hydroxyl group, cyano groupor methoxy group; and n shows 1 or
 2. 2. The salt according to claim 1,wherein X is divalent or trivalent residue of alkane having 1 to 30carbon atoms, or divalent or trivalent residue of monocyclic hydrocarbonor of bicyclic hydrocarbon having 3 to 30 carbon atoms, wherein —CH₂— inthe alkane may be substituted with —O— and one or more hydrogen atom inX is optionally substituted with alkoxy group having 1 to 6 carbonatoms, perfluoroalkyl group having 1 to 4 carbon atoms, hydroxyalkylgroup having 1 to 6 carbon atoms, hydroxyl group or cyano group.
 3. Thesalt according to claim 2, wherein the divalent or trivalent residue ofmonocyclic or bicyclic hydrocarbon in X is divalent or trivalent residueof monocycloalkane or bicycloalkane.
 4. The salt according to claim 1,wherein A⁺ is at least one cation selected from the group consisting ofthe formula (IIe), the formula (IIb), the formula (IIc) and the formula(IId), a cation of the formula (IIe):

wherein P²⁵, P²⁶ and P²⁷ each independently represent alkyl group having1 to 30 carbon atoms or cyclic hydrocarbon group having 3 to 30 carbonatoms, wherein one or more hydrogen atom in the alkyl group isoptionally substituted with hydroxyl group, alkoxy group having 1 to 12carbon atoms or cyclic hydrocarbon group having 3 to 12 carbon atoms andwherein one or more hydrogen atom in the cyclic hydrocarbon group isoptionally substituted with hydroxyl group, alkyl group having 1 to 12carbon atoms or alkoxy group having 1 to 12 carbon atoms, a cation ofthe formula (IIb):

wherein P⁴ and P⁵ each independently represent hydrogen atom, hydroxylgroup, alkyl group having 1 to 12 carbon atoms or alkoxy group having 1to 12 carbon atoms, a cation of the formula (IIc):

wherein P⁶ and P⁷ each independently represent alkyl having 1 to 12carbon atoms or cycloalkyl having 3 to 12 carbon atoms, or P⁶ and P⁷bond to form divalent acyclic hydrocarbon group having 3 to 12 carbonatoms which forms a ring together with the adjacent S⁺, and one or more—CH₂— in the divalent acyclic hydrocarbon group is optionallysubstituted with —CO—, —O— or —S—, P⁸ represents hydrogen, P⁹ representsalkyl having 1 to 12 carbon atoms, cycloalkyl having 3 to 12 carbonatoms or aromatic ring group optionally substituted, or P⁸ and P⁹ bondto form divalent acyclic hydrocarbon group which forms 2-oxocycloalkyltogether with the adjacent —CHCO—, and one or more —CH₂— in the divalentacyclic hydrocarbon group is optionally substituted with —CO—, —O— or—S—, a cation of the formula (IId):

wherein P¹⁰, P¹¹, P¹², P¹³, P¹⁴, P¹⁵, P¹⁶, P¹⁷, P¹⁸, P¹⁹, P²⁰ and P²¹each independently represent hydrogen atom, hydroxyl group, alkyl grouphaving 1 to 12 carbon atoms or alkoxy group having 1 to 12 carbon atoms,B represents sulfur atom or oxygen atom, and m shows 0 or
 1. 5. The saltaccording to claim 4, wherein the cation of the formula (IIe) is acation of the formula (IIf), (IIg) or (IIh):

wherein P²⁸, P²⁹ and P³⁰ each independently represent alkyl group having1 to 20 carbon atoms or cyclic hydrocarbon group having 3 to 30 exceptphenyl group, wherein one or more hydrogen atom in the alkyl group isoptionally substituted with hydroxyl group, alkoxy group having 1 to 12carbon atoms or cyclic hydrocarbon group having 3 to 12 carbon atoms andwherein one or more hydrogen atom in the cyclic hydrocarbon group isoptionally substituted with hydroxyl group, alkyl group having 1 to 12carbon atoms or alkoxy group having 1 to 12 carbon atoms; and P³¹, P³²P³³, P³⁴, P³⁵ and P³⁶ each independently represent hydoxyl group, alkylgroup having 1 to 12 carbon atoms, alkoxy group having 1 to 12 carbonatoms or cyclic hydrocarbon group having 3 to 12 carbon atoms, and l, k,j, i, h and g each independently show an integer of 0 to
 5. 6. The saltaccording to claim 4, wherein the cation of the formula (IIe) is acation of the formula (IIa):

wherein P¹, P² and P³ each independently represent hydrogen atom,hydroxyl group, alkyl group having 1 to 12 carbon atoms or alkoxy grouphaving 1 to 12 carbon atoms.
 7. The salt according to claim 6, whereinthe cation of the formula (IIa) is a cation of the formula (IIIe):

wherein P²², P²³ and P²⁴ each independently represent hydrogen atom oralkyl group having 1 to 4 atoms.
 8. The salt according to claim 1,wherein each of Q¹ and Q² is independently fluorine atom ortrifluoromethyl group.
 9. The salt according to claim 2, wherein X isdivalent or trivalent residue of alkane having 1 to 30 carbon atoms, ofcycloalkane having 3 to 10 carbon atoms or of norbornane, wherein —CH₂—in the alkane may be substituted with —O— and one or more hydrogen atomin X is optionally substituted with alkoxy group having 1 to 6 carbonatoms, perfluoroalkyl group having 1 to 4 carbon atoms, hydroxyalkylgroup having 1 to 6 carbon atoms, hydroxyl group or cyano group; Q¹ andQ² are both fluorine atoms; Y is hydroxyl group; and n shows
 1. 10. Thesalt according to claim 1, wherein the salt is the one of the formula(IIIa), (IIIb) or (IIIc);

wherein P²², P²³ and P²⁴ have the same meanings as defined in claim 7.11. A process for producing a salt of the formula (I)

wherein X represents divalent or trivalent residue of acyclichydrocarbon having 1 to 30 carbon atoms or divalent or trivalent residueof hydrocarbon having 3 to 30 carbon atoms which contains monocyclic orbicyclic ring, wherein —CH₂— in the hydrocarbon may be substituted with—O— and one or more hydrogen atom in X is optionally substituted withalkoxy group having 1 to 6 carbon atoms, perfluoroalkyl group having 1to 4 carbon atoms, hydroxyalkyl group having 1 to 6 carbon atoms,hydroxyl group or cyano group; Q¹ and Q² each independently representfluorine atom or perfluoroalkyl group having 1 to 6 carbon atoms; A⁺represents organic counter ion; Y represents hydroxyl group, cyano groupor methoxy group; and n shows 1 or 2, which comprises reacting an estercompound of the formula (IV)

wherein M represents Li, Na, K or Ag, and X, Y, Q¹, Q² and n have thesame meanings as defined above, with a compound of the formula (VII)A⁺Z⁻  (VII) wherein Z represents F, Cl, Br, I, BF₄, AsF₆, PF₆ or ClO₄,and A⁺ has the same meaning as defined above.
 12. A chemically amplifiedresist composition comprising a salt of the formula (1)

wherein X represents divalent or trivalent residue of acyclichydrocarbon having 1 to 30 carbon atoms or divalent or trivalent residueof hydrocarbon having 3 to 30 carbon atoms which contains monocyclic orbicyclic ring, wherein —CH₂— in the hydrocarbon may be substituted with—O— and one or more hydrogen atom in X is optionally substituted withalkoxy group having 1 to 6 carbon atoms, perfluoroalkyl group having 1to 4 carbon atoms, hydroxyalkyl group having 1 to 6 carbon atoms,hydroxyl group or cyano group; Q¹ and Q² each independently representfluorine atom or perfluoroalkyl group having 1 to 6 carbon atoms; A⁺represents organic counter ion; Y represents hydroxyl group, cyano groupor methoxy group; and n shows 1 or 2, and a resin which contains astructural unit having an acid-labile group and which itself isinsoluble or poorly soluble in an alkali aqueous solution but becomessoluble in an alkali aqueous solution by the action of an acid.
 13. Thecomposition according to claim 12, wherein each of Q¹ and Q² isindependently fluorine atom or trifluoromethyl group.
 14. Thecomposition according to claim 12, wherein the resin contains astructural unit derived from a monomer having a bulky and acid-labilegroup.
 15. The composition according to claim 14, wherein the bulky andacid-labile group is 2-alkyl-2-adamantyl group or1-(1-adamantyl)-1-alkylalkyl group.
 16. The composition according toclaim 14, wherein the monomer having bulky and acid-labile group is2-alkyl-2-adamantyl (meth)acrylate, 1-(1-adamantyl)-1-alkylalkyl(meth)acrylate, 2-alkyl-2-adamantyl 5-norbornene-2-carboxylate,1-(1-adamantyl)-1-alkylalkyl 5-norbornene-2-carboxylate,2-alkyl-2-adamantyl α-chloroacrylate or 1-(1-adamantyl)-1-alkylalkylα-chloroacrylate.
 17. The composition according to claim 12, wherein thecomposition further comprises a basic compound.
 18. The compositionaccording to claim 12, wherein X is divalent or trivalent residue ofalkane having 1 to 30 carbon atoms, or divalent or trivalent residue ofmonocyclic hydrocarbon or of bicyclic hydrocarbon having 3 to 30 carbonatoms, wherein —CH₂— in the alkane may be substituted with —O— and oneor more hydrogen atom in X is optionally substituted with alkoxy grouphaving 1 to 6 carbon atoms, perfluoroalkyl group having 1 to 4 carbonatoms, hydroxyalkyl group having 1 to 6 carbon atoms, hydroxyl group orcyano group.
 19. The composition according to claim 18, wherein thedivalent or trivalent residue of monocyclic or bicyclic hydrocarbon in Xis divalent or trivalent residue of monocycloalkane or bicycloalkane.20. The composition according to claim 12, wherein A⁺ is at least onecation selected from the group consisting of the formula (IIe), theformula (IIb), the formula (IIc) and the formula (IId),

wherein P²⁵, P²⁶ and P²⁷ each independently represent alkyl group having1 to 30 carbon atoms or cyclic hydrocarbon group having 3 to 30 carbonatoms, wherein one or more hydrogen atom in the alkyl group isoptionally substituted with hydroxyl group, alkoxy group having 1 to 12carbon atoms or cyclic hydrocarbon group having 3 to 12 carbon atoms andwherein one or more hydrogen atom in the cyclic hydrocarbon group isoptionally substituted with hydroxyl group, alkyl group having 1 to 12carbon atoms or alkoxy group having 1 to 12 carbon atoms, a cation ofthe formula (IIb):

wherein P⁴ and P⁵ each independently represent hydrogen atom, hydroxylgroup, alkyl group having 1 to 12 carbon atoms or alkoxy group having 1to 12 carbon atoms, a cation of the formula (IIc):

wherein P⁶ and P⁷ each independently represent alkyl having 1 to 12carbon atoms or cycloalkyl having 3 to 12 carbon atoms, or P⁶ and P⁷bond to form divalent acyclic hydrocarbon group having 3 to 12 carbonatoms which forms a ring together with the adjacent S⁺, and one or more—CH₂— in the divalent acyclic hydrocarbon group is optionallysubstituted with —CO—, —O— or —S—, P⁸ represents hydrogen, P⁹ representsalkyl having 1 to 12 carbon atoms, cycloalkyl having 3 to 12 carbonatoms or aromatic ring group optionally substituted, or P⁸ and P⁹ bondto form divalent acyclic hydrocarbon group which forms 2-oxocycloalkyltogether with the adjacent —CHCO—, and one or more —CH₂— in the divalentacyclic hydrocarbon group is optionally substituted with —CO—, —O— or—S—, a cation of the formula (IId):

wherein P¹⁰, P¹¹, P¹², P¹³, P¹⁴, P¹⁵, P¹⁶, P¹⁷, P¹⁸, P¹⁹, P²⁰ and P²¹each independently represent hydrogen atom, hydroxyl group, alkyl grouphaving 1 to 12 carbon atoms or alkoxy group having 1 to 12 carbon atoms,B represents sulfur atom or oxygen atom, and m shows 0 or
 1. 21. Thecomposition according to claim 20, wherein the cation of the formula(IIe) is a cation of the formula (IIf), (IIg) or (IIh):

wherein P²⁸, P²⁹ and P³⁰ each independently represent alkyl group having1 to 20 carbon atoms or cyclic hydrocarbon group having 3 to 30 exceptphenyl group, wherein one or more hydrogen atom in the alkyl group isoptionally substituted with hydroxyl group, alkoxy group having 1 to 12carbon atoms or cyclic hydrocarbon group having 3 to 12 carbon atoms andwherein one or more hydrogen atom in the cyclic hydrocarbon group isoptionally substituted with hydroxyl group, alkyl group having 1 to 12carbon atoms or alkoxy group having 1 to 12 carbon atoms; and P³¹, P³²P³³, P³⁴, P³⁵ and P³⁶ each independently represent hydoxyl group, alkylgroup having 1 to 12 carbon atoms, alkoxy group having 1 to 12 carbonatoms or cyclic hydrocarbon group having 3 to 12 carbon atoms, and l, k,j, i, h and g each independently show an integer of 0 to
 5. 22. Thecomposition according to claim 20, wherein the cation of the formula(IIe) is a cation of the formula (IIa):

wherein P¹, P² and P³ each independently represent hydrogen atom,hydroxyl group, alkyl group having 1 to 12 carbon atoms or alkoxy grouphaving 1 to 12 carbon atoms.
 23. The composition according to claim 22,wherein the cation of the formula (IIa) is a cation of the formula(IIIe):

wherein P²², P²³ and P²⁴ each independently represent hydrogen atom oralkyl group having 1 to 4 atoms.
 24. The composition according to claim18, wherein X is divalent or trivalent residue of alkane having 1 to 30carbon atoms, of cycloalkane having 3 to 10 carbon atoms or ofnorbornane, wherein —CH₂— in the alkane may be substituted with —O— andone or more hydrogen atom in X is optionally substituted with alkoxygroup having 1 to 6 carbon atoms, perfluoroalkyl group having 1 to 4carbon atoms, hydroxyalkyl group having 1 to 6 carbon atoms, hydroxylgroup or cyano group; Q¹ and Q² are both fluorine atoms; Y is hydroxylgroup; and n shows
 1. 25. The composition according to claim 12, whereinthe salt is the one of the formula (IIIa), (IIIb) or (IIIc);

wherein P²², P²³ and P²⁴ have the same meanings as defined in claim 23.